Hi all,
It "works" is a relative term. An 8 cylinder car running on 5 cylinders
still "works"
In the process of learning about antennas the fine points should include:
1. A good front to back ratio on the receive side to reduce ground noise.
2. The satellite band is very narrow so some sacrifice of front to back
ratio for the 2 M side for an additional 1.5 dB of gain may help in marginal
conditions.
3. Insulation of the boom to the elements will reduce losses, and lower
frequency. If elements make good solid contact to the boom and are tuned to
the right frequency this loss is very small.
4. Changes in conductivity of element to boom contact will cause performance
to vary.
5. If there is any corrosion on any electrical contact area of the antenna,
including boom to element contact, receiver blocking can occur. Avoid using
dissimilar metals to prevent corrosion.
6. Most of the fun is finding solutions to these problems. Start by looking
at how antennas are built. There are some very clever designs of antennas in
the market place. Many of these problems have already had multiple solutions
applied.
Art,
KC6UQH
-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of David Donaldson
Sent: Saturday, December 27, 2008 10:24 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: Fw: ELK or ARROW
The issue is really application of the antenna. A poor antenna in this case
is using one where it's not designed for. Just because something costs less
does not mean it will NOT work in the application you have for it (double
negative). For example a high gain boom antenna will work poorly as a
handheld antenna due to it narrow beamwidth and in ability to point at
target.
Case in point, we can all drive Suburban's because there is 10" of snow on
the ground but why? A Camry will work just as well if all I need is to
travel main highways.
I know that based on using the Arrow holding by hand it is better then a
dipole so it at least better then about 2.15dbi and using it I know that I
can get at least twice the RX power when pointed down it's boresite so it's
about 3db of gain over the dipole (0 dBd). That would make it ABOUT 5 db.
I would like to see the plots of the patterns of the tests done on the
arrow, also what the range looked like and equipment used. I have seen
commercial antenna companies' mess up antenna measurements. Properly done
engineering tests will align with what is experienced in the field, if it
doesn't then its an oops. 4dBi would mean not much better then a wet
noodle....
Point: The arrow works well for its application and is worth the money if
your application is a handheld or simple tripod mounted antenna. I say it's
is worth the money because it works.
73,
Dave
Burnsville, MN
WB7DRU; NNN0AXK
-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Jim Danehy
Sent: Saturday, December 27, 2008 8:35 PM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Fw: ELK or ARROW
. there is the old adage that you get what you pay for . . . why buy a
poorly designed antenna that does not work very well
> ?
>> If you have a 5 element yagi that only produces 4 dbi you are not getting
> what you paid for . . . most 2 element yagis would out perform that
> statistic . . . a 5 element yagi should be at least 9 db + or 10 db dbd
> (dipole ) not isotropic . . . . there is something that is called
> MERCHANTABILITY . . .i.e., an IMPLIED WARRANTY that you are getting at
> least the minimum for your money . . .
> 4 dbi for an Arrow is way off base . . . so it is not just ; you can not
> afford a Cadillac but you are not even getting a Ford or Chevy . . i.e.,
> the gain of a 5 element yagi on 435 mhz . . . that is the issue, not cost
> alone . . . . . . same comments apply to the ELK but I have attempted to
> make the point that there is a minimum performance for a certain number of
> elements that is pretty OBJECTIVE and when it is not met . . . . well
> that is my point . . . these two antennas have shown to some testers that
> they do not measure up to the minimum EXPECTATIONS . . .unfortunately that
> is acceptable to some . . . . then it becomes acceptable to many . . .
> and objectivity is abandoned . . .
>> Jim W9VNE
>>> ----- Original Message -----
> From: "Trey Brown" <palintheus at gmail.com>
> To: "Jim Danehy" <jdanehy at cinci.rr.com>
> Sent: Saturday, December 27, 2008 6:39 PM
> Subject: Re: [amsat-bb] ELK or ARROW
>>>> Thanks for the comments. Realize, though, that not everyone wants or
>> can afford to have the Cadillac.
>>>>>> On Sat, Dec 27, 2008 at 4:06 PM, Jim Danehy <jdanehy at cinci.rr.com> wrote:
>>> the Arrow antenna has been critiqued by Kent Britain, WA5VJB
>>>>>>http://wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf>>>>>> he says that some have measured the Arrow for gain on 435 mhz @ 4 dbi
>>> (isotropic) . . . . and that further analysis showed that for the
>>> element lengths used on 435 mhz that it peaks at 457 mhz and not 435 mhz
>>> . . . Kent is a well respected VHF/UHF antenna person who has plenty of
>>> credibility . . .
>>>>>> Kent opines that the Arrow, as built does not have its elements
>>> insulated from the boom. It uses dimensions for insulated elements . . .
>>> so much for the Arrow . . . .
>>>>>> Now for the ELK : a local friend of mine owns an Arrow and he uses it
>>> successfully. He bought an ELK and attempted to compare the Arrow and
>>> the ELK . . . . he could not make an across town QSO on 435 mhz from his
>>> second story window with the ELK , so he sent the ELK back for a refund
>>> .
>>>>>> I have worked and exchanged QSLs with several hundred satellite users .
>>> . .the majority of the folks that have worked and QSLed me (close to 250
>>> + ) have been using either the Arrow or ELK based upon the information
>>> on their cards. So they are popular. Are they optimum ? A lot of
>>> anecdotal information would seem to say NO . . .
>>>>>> Thirty-five years ago I worked Oscar 6 with a homebrew 2 mtr yagi that
>>> probably was worse than either the Arrow or Elk but I worked YV and KL7
>>> from Indiana on CW with about 15 watts to the 3 elements which my XYL
>>> waved around at my directions . . . not any more . . .what do I use
>>> these days : a pair of circular polarity yagis on 10 foot booms
>>> manufactured by M Square . . . .
>>>>>> Folks ask what should they buy ? Maybe a Ford or maybe a Chevy . . .
>>> neither is a Cadillac . . . .
>>>>>> Jim W9VNE
>>> _______________________________________________
>>> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
>>> Not an AMSAT-NA member? Join now to support the amateur satellite
>>> program!
>>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb>>>>>>>>>>> --
>> Trey -- N5THX
>>>> They who can give up essential liberty to obtain a little temporary
>> safety, deserve neither liberty nor safety.
>> - Benjamin Franklin
>>>
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